DE 101 60 717 A1 (U.S. Pat. No. 7,144,346 B2) discloses a torsion angle sensor for measuring the torsion angle of two shafts coupled with one another.
A preferred application for the present invention is in the steering systems of motor vehicles, in which the forces exerted on the steering assembly as torque are also measured. For example, a steering gear shaft connected to the steering wheel of a motor vehicle is coupled via a torsion bar to a pinion shaft, which is connected to the steering gear. Torque that is generated between steering gear shaft and pinion shaft twists the torsion bar, causing steering gear shaft and pinion shaft to rotate in opposite directions. The relative twisting of steering gear shaft and pinion shaft is referred to as the torsion angle. This torsion angle corresponds to the torque acting on the torsion bar.
The process of measuring the angle of rotation of the two shafts in relation to a reference angle is known in the prior art. The difference between the two measured angles then corresponds to the torsion angle. This measurement can be taken magnetically (US 2003/0062890 A1, DE 100 60 287 A1), optically (DE 100 41 095 A1) or generally using other rotational position sensors (DE 101 60 717 A1, DE 198 34 322 A1, DE 10 2007 058 657 A1, EP 1 925 533 A1, DE 102 45 975 A1, FR 2 563 795 A1).
In general, however, with all known torsion angle sensors a difference signal must be generated from at least two sensors, requiring the use of a computing system; the use of at least two sensors also increases the probability of failure.
In DE 102 45 975 A1, the steering gear shaft and the pinion shaft are coupled with one another via a double planetary gear set to form a power steering mechanism, specifically such that a first planet carrier is non-rotatably connected to the steering gear shaft and a second planet carrier is non-rotatably connected to the pinion shaft. The two sun gears of the planetary gear set are also connected to one another there. The internal gear of the planetary gear set that is coupled to the steering gear shaft is non-rotatable. The internal gear of the internal gear that is connected to the pinion shaft is movable and can be actuated or impeded to generate power steering. To measure the torsion angle between steering gear shaft and pinion shaft, however, two separate rotational angle sensors are also provided, with one of these being connected to the steering gear shaft and the other to the pinion shaft.